Narrower Definition for 'Full Term' Pregnancy Reflects New Understanding, Authors Say

A new, narrower definition for a full term pregnancy released by the American College of Obstetricians and Gynecologists (ACOG) reflects increased understanding regarding the final weeks of pregnancy, those behind the change say.

In the past, a full term pregnancy was one that lasted between 37 and 42 weeks. However, as Dr. Jeffrey Ecker, chair of the ACOG that revised the labels, told The Associated Press, "Weeks matter."

For this reason, "early term" will now refer to any child born during the 37th or 38th week of pregnancy while the label "full term" is one that will be reserved for those deliver during the 39th or 40th week. Any babies born during the 41st week will be "late term" and any after that "post term."

According to the statement issued regarding the decision, the changes are meant to reflect recent research highlighting the importance of the last few weeks of pregnancy, during which the baby's brain and lungs are still maturing.

"Until recently, doctors believed that babies delivered in this five-week window had essentially the same good health outcomes," Ecker said in a statement.

Those babies born between 39 weeks and 40 weeks six days experience the best health outcomes when compared to those born before or after this period, the researchers note, prompting them to declare this window as full term.

"This terminology change makes it clear to both patients and doctors that newborn outcomes are not uniform even after 37 weeks," said Jeffrey L. Ecker, MD, chair of The College's Committee on Obstetric Practice. "Each week of gestation up to 39 weeks is important for a fetus to fully develop before delivery and have a healthy start."

Planned deliveries prior to 39 weeks should only occur in the case of serious health risks for either the fetus or mother, Ecker said.